Telegraph switching system



10 Sheets-Sheet 1 w. M.. BACON v Filed Sept. 24, 1945 Dec. 10, 1946.

' TELEGRAPH swITcHING SYSTEM Dec. 10, 1946.

W. M. BACON TELEGRIAPH SWITCHING SYSTEM Fild Sepp. 24, 1945 10Sheets-Sheerl 2 ML Y .Fut

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` TELEGRAPH SWITCHING SYSTEM 4 Filed sept. 24, 1945 1o sheets-sheet 3 REC 'G EPERE ATTORNEY Dec. 10, 1946. w, M BACON I 2,412,198

TELEGRAPH i SWITCHING SYSTEM Filed Sept, 24v, 1943 10 Sheets-Sheet 4 o ono RECYCLE /NvE/VTQR n. M BACON A TTORNEV Dec. 1o, 1946. ,w. M, BACON2,412,198

'IELEGRAPH SWITGHING SYSTEM Filed Sept. 24, 1945 lO Sheets-Sheet 5/NVE/v TOR W M. BA CON ATTORNEY 10 Sheets-Sheet 6 w. M. BACON Fied sept.-24, 1943 'ELEGRAPH SWITCHIG SYSTEM' Hun MW w W RM m v @yN/J m mM?. .I\0 e, W W Qm r.| W h m2 m/ rl ww 1| mi, im EN 1 we all. :um MNH.- h No RKF M- h n. nimm@ #Vw-j 1E/l uw r N Ij fil #MJ p L Dec. 1G, 1946.

W. M. BACON TELEGRAPH SWITCHING SYSTEM Filed sept. 24, 1945lorsheets-sheet 7 /NVENTOR W M BACON Arron/ver Dec. 1o ,'-1946. l W, M,BACON l 2,412,198

A TELEGRAPH' SWITCHING SYSTEM Filed sept. 24 A1943 1o shers-sheet e /NVEN TOR c w M. 5,4 co/v By 'fd/@ JW.

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w.' M. BACON TELEGRAPH SWITCHING SYSTEM Dec. 1o, 1946..

Filed Sept. 24, 1945 Q ...El

W5/v 7'0/5 WBACON sry@ 'z i f ATTORNEY Dec. 10, 1946. w. M. BACONTELEGRAPH SWITCHING SYSTEM lO Sheets-Sheet lO Filed Sept. 24, 1945SKS... $5.35 SEQ.

/NVENTOR W M. BACON ATTQQNEY Patented Dec. 10, 1946 TELEGRAPH sWITCHINGSYSTEM Walter M. Bacon, New York, N. Y.,hassignor to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkApplication September 24, 1943, Serial No. 503,599

18 Claims.

This invention relates to communication systems and more particularlyIto automatic telegraph switching systems in which storage controlledtransmitting apparatus at outlying telegraph stations is automaticallyset into operation for transmitting stored messages from the outlyingstations to the central switching station under control of equipment atthe central switching station.

The object of the present invention is to provide an improved telegraphsystem with increased flexibility in the manner of controllingYtransmission from a plurality of outlying transmitters to a centralswitching station.

In accordance with an exemplary embodiment of the invention, the systemdisclosed in United States patent application, Branson et al.. SerialNo. 448,878, led June 27, 1942, has been improved to increase theilexibility of lthe control arrangementA for initiating the transmissionof messages from the outlying stations to the central switching station.

In accordance with the system disclosed in the said Branson application,means are provided to enable the operator or attendant at the centralswitching station to manually at willr start the transmission of anytransmitter associated with any of thev lines extending from the centralswitching station,'provided. that line is not engaged in thetransmission of a message from some transmitter to the central switchingstation. Means are also provided to interrupt transmission from anytransmitter toward the central switching station and thereafter initiatetransmission from any other transmitter. In that application, means arealso disclosed for automatically testing these transmitters for storagematerial available for transmission to the central switching station andinitiating transmission from transmitters which are provided with suchmaterial in rotation one at a time.

In the system disclosed in said` Branson application means are alsoprovided for Itesting and initiating transmission from certain of thetransmitters more often .than from others of the transmitters. Thismeans, however, requires extensive wiring changes. and at times theutilization of an individual code for each turn given to any transmitterin the complete cycle ofv testing all of the transmitters. In additionin said application manual means are provided for preventing the testingand initiation of transmission of any oneY or more of the transmitters.

In accordance With this previous application,V

the system is arranged so that the transmitters are tested in the sameorder during each cycle of operation and the same number of times,unless a manual operablekey individual to each transmitter has beenoperatedv or released.

In accordance with the present invention, means are provided forautomatically changing the order and frequency of testing of the varioustransmitters in cyclic order without requiring the necessity of changingsolder connections, without manually operating any key individual toeach of the transmitters andrwithout requiring an individual codecombination or group of code combinations for each turn or Itest of atransmitter during a cycle of operation. In other Words, a feature ofthe present invention relates to provision of an automatic skip circuitwhich may be arrangedy to cause the transmitter start or controlequipment to automatically'skipany one 0r more of the transmittersassociated with any line during any cycle operation of the transmitterstart circuit.

Thus, in accordance with the present invention, means are provided forautomatically varying the frequency and/or order of testing the varioustransmitters associated with any of the partylines, thus enabling thetrafc from theV various stations. to be handled most expeditiously and,enabling the system toHbe operated at its highest eiiiciency.

A feature' of theV present invention relates to apparatus forincorporating the above apparatus and features embodyingv the presentinvention in the system disclosed in said Branson' application withoutinterfering` with or eliminating any of the features of the. systemdescribed in said above-identified copending Branson application.

The foregoing objects and features of the present invention, the novelfeatures of which are specifically set forth in the-claims appendedhereto, and maybe more readily'understoo'dfrom the following descriptionwhen read with reference to the attached drawings, in which:

Fig. lA shows the manner in which Figs, 2, 3f and ishould-be arrangedadjacent one"y another to show in outline form various cir-cuits andequipment of an exemplary system in accordance with the presentinvention as Well as to illustrate the' routes'of messages through thesystem;

Fig. l-B shows the manner in which Figs. 5 through 1'1 inclusiva, shouldbe arrangedA adjacent one. another toshowfth'e circuit arrangements indetail in. exemplary form ofthe invention;

Figs. 2, 3 and 4 when arranged asf shown in Fig.

1A show in outline form a typical system embodying the presentinvention; and

Figs. 5 through 11, inclusive, when arranged as shown in Fig. 1B show indetail the various circuits comprising an exemplary embodiment of thepresent invention. Figs. 5 through 11, inclusive, show in detail thecircuits indicated in outline form in the heavy line 350 of Fig. 3.Furthermore, said Figs. 5 through 1l', inclusive, of the presentapplication may be substituted without material alteration for Figs. 14,l5, 16, 17, 18, 19 and 20 of said Branson et al. application.. SaidFigs. 5 through 11 may also be substituted for other figures of saidBranson application associated with the half-duplex line withoutmaterial modification.

Referring now to Figs. 2, Sand 4 when arranged as shown in Fig. 1A, Fig.2 shows two typical .l

party lines and the station and control equipment associated therewith.One party line is designated .2m-which comprises a receiving chan-` nel2H and' aftransmitting channel 2I2. larly, party line 26D comprises areceiving channel 26| and a transmitting channel 262. Both transmittingand receiving channels are illustrated in Fig. 2 and also Fig. 3 bymeans of'telegraph lines or conductors. It is to be understood, however,

that these lines or channels may include any type' of telegraphtransmission equipment normally l clude or comprise any or all of theforegoing types of transmission systems or any or all combinationsofsuch 4types of transmission systems.

The transmission systems of the various types comprising the party linesoperate in their usual and well understood manner so a description ofVthe operation thereof need not be included herein because it would serveno useful purpose and 'only tend to obscure-the other elements andfeatures of thevpresent invention.`

Each ofthe party-lines shown inFig. 2 extends to a plurality of outlyingsubscriber or way stations.` It is to be understood also that it iswithin the scope of this invention to extend lines individually from oneor more of the outlying stations to the central switching exchange. Inthis case certain of the control equipment associated with each of theparty lines need not be provided as will be@ readily the'art.

Each of the lines whichextends to more than oneoutlyingl station isprovided with control equipment located at or near the outlying stationsof the party line. Control equipment maybe provided which is individualto each of the outlying or way stations in case theway stations arerather widely4 separated or the control equipment'may be providedcommento a group of outlying static-,ns which vare located morecloselytogether. In

addition,A certain of the control equipment mayl be individual Vtocertanoutlying stations, While other control equipment provided` for the sameparty line may be common outlying stations.

Simiapparent to thoseskilled inV to a plurality Qfftne sets of switchingand controlling circuits, somek y times referred to as a secondaryswitching center, are associated with each of the party lines. Forexample, party line 210 extends to the switching and control circuits orsecondary switching centers 2|3, 2M and 2I5. The control equipment 2l4is individual to a station at 2l9. Control equipment 2 I5 is common tostations 2 I6, 2H and 2l8, while control equipment 2l3 is common tostations 22H to 224 inclusive. Each of the outlyingl stations isprovided with a receiving instrument, a transmitting equipment, andcontrol equipment. In the specific system described herein, thetransmitting equipment comprises a keyboard perforator for perforatingpaper tape in accordance with the signals to be transmitted and a tapecontrolled transmitter for transmitting signals in accordance with theperforations in the tape. For example, at station 2l6 thereceiving'instrument and the keyboard perforator is illustrateddiagrammatically and designated 225 in Fig. 2, the transmittingdistributor is designated 235, while the control equipment is designated236. Similar equipment is provided at the other stations. In addition,station 219 is provided with a receiving recorderV or reperforator foragainr perforating tape in accordance with messages received from thesystem. This reperforator is provided at those stations at which othertelegraph lines or circuits may terminate so that the messages intendedfor stations connected to these other lines may be' recorded at station2|@ and later automatically transmitted over the proper line withoutrequiring the time of an operator to retransmit the message.

In order to transmit messages over this system, the attendant orsubscriber at the outlying or way stations perforates messages in papertapes for later transmission over the system. Preceding each message, anaddress or group of switching signals is perforated in the tape andfollowing each message an end of message orV disconnect signal is alsoperforated in the tape. Following the end of messagesignal, thesubscriber may perforate any address signal followed by another messageintended for the station designated by the address. Following thismessage and eachof the messages, the operator will then perforate adisconnectsignal` in the tape. Furthermore, the operator or attendantwill usually perforate Yan end of transmission signal inthe tape` afterthe disconnect signal following the last message available fortransmission from the station then transmitting. Y

' The attendant or operator at the outlying station will then insert atape in the transmitter forY forator v4| I,va monitoring receivinginstrument 1 410,' transmitter or transmitting distributor M2,controlrelays 4l3 and a director circuitdl. Fig. 4-also`shows'amiscellaneous intercept circuit 421 and a receiving reperforatorAZSand.a tape receptaclev425. A` wilful 'intercept circuit 424 is also. shown.This intercept circuit is provided with a repeating instrument420'comprislng a recorder or reperforator 42| and a' transmitting device422. A director 423 is also associated with the wilful interceptcircuit.

Each of the party lines Iterminating at the switching office or centeris provided with an incoming line .circuit 322 and a receiving onlymachine 323, a storage repeater 324 and associated transmitter 325.Incoming line circuit 322 causes the messages intended for the centralswitching station to be lrecorded on the receiving only receiver 323 andcauses the messages intended for other stations of the system to berecorded by the reperforator 326. Director circuit 321 is associatedwith :the transmitter 325 and serves to connect the transmitter 325selectively lto any of the llines terminating at the central switchingstation under control of the address characters preceding each message.

Each of the party lines is also provided with .transmitter startcircuits, such as 3|0, and outgoing line circuits and equipment fortransmitting messages over the party line. An outgoing line circuit isassociated with party line 2 l0. Briefly, messages directed to stationsof party line 2|I are transmitted to storage repeaters associated withline 2| under control of the director circuits of the lines upon whichthe messages originate for later transmission over the outgoing lines.

Figs. 2 and 3 also showa .trunk circuit 299 comprising two transmissionchannels 29| and 292 extending to a distant switching center 295. Theterminal equipment associated with the trunk circuits is similar to theterminal equipment asso ciated with each of the party lines as describedabove.

' The operation of the various circuits referred to above is describedin detail in the above-identied copending patent application of Bransonet al. Since the respective circuits referred to above forming parts ofthe system referred to herein operate in substantially the same manneryas described above in said patent application of Branson et al., whichpatent application has been made a part hereof as if fully includedherein, a more detailed'description has therefore not been repeated.

As stated above, the attendants at the outlying stations will insert thetape in the tape control transmitters located at .the respectivestations. Thereafter the operator at the central switching station willmanually set into operation the transmitter start .circuit which willcause certain signals to be transmitted over the receiving channel ofthe respective party lines for testing the transmitters associatedthere-with and initiating operation of these transmitters which aresupplied with storage material available for transmission.

In the system described in the above-identified application of Bransonet al., it is necessary for the operator to start or initiate theoperation in the transmitter start circuit manually the first time eachday. Thereafter the operator may operate an automatic key which willcause the transmitter start circuit to automatically .test thetransmitters associated with the respective` party lines in rotation.Means are also provided for enabling the operator by the operation of amanual key to prevent the testing of :any one or more of thetransmitters associated with the respective party lines.

In accordance with the present invention an additional key and group ofcircuits and apparatus are provided which will automatically cause the.skipping of .the testing of certain of the transmitters associated withany' party line during certainv cycles of operation of .the transmitterstart circuit. According to the present invention the automatic skipfeature is m-ade ilexibleso that the testing of different transmit-tersmay be skipped during diiferent cycles of operation of the transmitterstart circuit. In this way an extremelyflexible arrangement is providedfor controlling the transmission from the respective transmittersassociated with the party line. Not only may the order of testing bevaried at will but also the frequency or relative frequency of testingand initiation of operation of the transmitters may be readily variedduring any cycle cf operation of the transmitter start circuit inaccordance with any predetermined plan or system.

The circuit details of one exemplary embodiment of the invention showinghow the varying of the frequency of testing of the transmitter `may beaccomplished in accordance with the present invention is shown in Figs.5 through 1l, inclusive, when arranged adjacent one another as shown inFig. 1B,

Inasmuch as the present invention relates more particularly to theautomatic operation of the transmitter start circuit, the operation of.this cir-cuit under manual control will not be repeated here since itis described in detail in the aboveidentified application of Branson etal. incorporated herein and to which reference is made for a detaileddescription of the operation of the circuit under manual control. i

Assuming for purposes of illustration that the circuit has been set intooperation and transmission has been started from some one ofthetransmitters associated with the party line to which the transmitterstart circuit shown in Figs. 5 through 1l, inclusive, is connected.Under these conditions the stepping switch comprising brush arms 50|through 506, inclusive, has been advanced Ito the No. 5 position bymeans of magnet 501 in .the manner set forth in the above-identiedapplication of Branson et al. Similarly, the stepping switch comprisingbrush arms 508 to 5| 3 as well as the stepping switch :comprising arms 55 and 5 6 have stepped to terminals assigned to |the transmitter whichhas been set into operation. In addition, relay 656 and 601 and 609 aremaintained operated so long as the transmitter set into operationcontinues to transmit signals to the central switching station. Assumingfurther for the purpose of illustration that the automatic start key 5|9has lalso been operated after the transmitter has been set in-tooperation.` Under these circumstances, a circuit is completed for theoperation of relay 608 which relay remains operated as long as theautomatic key 5 I 9 remains operated. Further assume that the steppingswitches comprising brushes 51| to 511, inclusive, have been positionedin the position shown in the drawings in any suitable manner such as.will be described hereinafter. l

During the transmission of signals from any of the transmitters of theparty line, a ground connection is maintained to lead 2136 by theincoming line circuit in a manner described in the above-identifiedapplication of Branson et al.

conditions vas set forth in the above-identiiiedapplication of Bransonet al., the incoming line circuit of the party line in which thetransmitter start circuits in Figs. to 11, inclusive, will remove groundfrom lead 2136 and thus permit relay 606 to release. The release ofrelay .606 completes a circuit for the operation of relay 6| I at thistime. Relay 6|| in operating. causes the C stepping switch comprisingbrush arms 50| to 506, inclusive, to be stepped to its initial position.A detailed description including the tracing of the circuits of thevarious relays and the times of operation thereof during the return ofthis switch to its initial position has not been repeated here becauselit is clearly set forth in the above-identied application of Branson etal. and inasmuch as the circuit works in substantially the same mannerat this time, littleyif anything, can be gained by further socomplicating the present disclosure.

. During the return of the stepping switch comprising brush arms 50| to506, inclusive, to its initial position or to a position equivalent toits initial position, various relays may operate. However, theYoperation ol these relays at this time is without. significance.Consequently, their operation need not be described at the present time.

When the C stepping switch returns to its No. 1 position, relay 6||releases and prevents the further advance of the switch at this time.The return of this switch to its No. 1 position completes a circuit kforthe operation of relay 10| which relay operates and completes a circuitfor the operation of relay 102. Relay 102 in operating completes acircuit for maintaining itself operated under control of various relaysincluding relay 606. The operation of relay 102 completes a circuit forthe operation of relay 80|, the operation of which relay stops theoperation of either of the transmitting instruments shown in Figs. l0and 11. The operation of relay 80| interrupts the circuit of releasemagnets of these transmitters and thus insures that the transmitter willcome to rest at the completion of the code combination then in progressof transmission over the party line.

The operation of relay 102 in addition removes ground from theright-hand terminal of condenser 1|| and permits this terminal to becharged from battery 1|6 through high resistances 55| and 533 inparallel. Condenser 1I| is connected through high resistance 1|5 to thegrid of .tube 1|0. By a proper choice of the values of resistances 1| 4as well as the constants of tube 1I0, the size of condenser 1| I, andpotential battery 1|6`4of the anode path through tube 1|0, this vtube ismaintained non-conductive so long as ground is connected to theright-hand terminal of condenser 1|| and for an appreciable interval oftime thereafter until the right-hand terminal of condenser 1|| ischarged to a predetermined positive potential. In an exemplaryernbodiment of the present invention, the values of the resistances 55|and 533, the size of condenser 1| the constants of tube 1|0, and thevalue of resistance 1|4 have beenselected so that it requiresapproximately .'1 of a second after ground is removed from theright-hand terminal of condenser 1|| for tube'1l0 to pass suiiicientanode current to operate relay 103. This .7 of a second allows ampletime for either of the transmitting instruments shown in Fig. 10 or 11to complete the transmission of the code combination l out above, beforerelay 602 releases.

`lease of relay 602 in turn causes the release off in progress oftransmission at the time relay for maintaining relay 10| operated andalso com.

pletes a circuit for the operation of either relay 9|4 or 923, dependingupon which of the two transmitters shown in either Fig. 10 or l1 was thelast to transmit. If the transmitter shown in Fig. lf2-was the lasttransmitter to transmit relay =9:|4 will operate whereas if thetransmitter shown in Fig. 11 was the last transmitter to transmit, relay923 will operate. The operation of either one or the other of theserelays prepares circuits for the operation of the correspondingtransmitter under control of the transmitter start circuit as will bedescribed hereinafter. The operation of relay 602 also completes acircuit for the operation of relay `603 which relay in turn completes acircuit for the operation of stepping magnet 5|4. The brush arms 508 and5|3 do not advance at this time, however, because they advance upon therelease of magnet 5|4 and not upon the operation thereof.

The operation of relay 602 also completes a circuit for the operation ofthe stepping magnet 501 but the associated brush arms 50| through 506 donot advance at this time. However, the operation of the stepping magnet501 removes the short circuit from around the upper winding of relay 104and permits this relay to operate. The operation of relay 104 completesa circuit for` maintaining itself operated under control of relay 602.The operation of relay 104 interruptsthe operating circuit from thestepping magnet 501` which permits magnet 501 to release and advance thebrush arms 50| through 506 one step to their No. 2 position. Brush arm50| in advancing one step interrupts the operating circuit of relay 603and thus permits relay 603 to release and in turn releases steppingmagnet 5|4. The release of stepping magnet 5|4 causes the brush arms 508through 5|3, inclusive, to advance one step and thus partially conditionthe transmitter start circuit fcr transmission of the nal code in thetransmitter start pattern which designates the transmitter that is to betested and set into operation by the transmitter start circuit if it isprovided with storage material available for transmission. The advanceof brush arm 5|2 at this time also interrupts the locking circuit ofvrelay 609. The release of relay 609 completes a cir cuit for theoperation of relay 105.

The operation of relay 104 again connects ground to the right-handterminal cf condener 1|| and thus to the grid of tube 1i0. As statedabove, with ground connected to the grid of tube 1|0 the anode-cathodepath is blocked so that relay 103 will release and in turn cause therelease of relay 602. Relay Yi502, howevery is slow in releasing so thatvarious circuits and relays will have sufficient time to function, aspointed The rerelay 104.

- The release of relay 602 at this time completes a circuit for theoperation of either the distributor release magnet |041 or Hill,depending upon which of the transmitters was previously transmitting.Assume for the purpose of illustration relay 9|4 previously operated dueto the fact that the transmitter shown in Fig. 10 was the lasttransmitter to transmit prior to the 'operationsof relayV 00|. Underthese circumstances theidistributor release magnet |041 will operateupon the release of relay 602. The operation of the distributor releasemagnet |041 at this time releases the distributor shaft I05| forrotation through one revolution. During the rotation through thisrevolution a blank code combination, that is, a code combination inwhich all the impulses are spacing, is transmitted over the receivingchannel oi party line 2I0.

Near the beginning of the revolution ci shaft |05! the auxiliarycontacts |050 are closed and complete a circuit for the operation ofrelay 605 which relay operates and completes a circuit'for maintainingitself operated under control of relay 602. The operation of relay 605interrupts the operating circuit of magnet |041 thus insuring that thismagnet will release and stop the distributor shait I 05| at the end ofthe revolution during which the blank code combination has beentransmitted.

IThe release of relay 602 removes ground from the right-hand terminalofv condenser 1I I, which condenser again starts to charge from battery1I6 through the high resistances 55| and 553, as described above.

If the terminal upon which brush arms 508 through 5|5, inclusive, havebeen advanced to and are resting upon during the time brush arm 50| isin its No. 2 position has been assigned to a station upon which one ofthe skip keys 54| through 550, inclusive, has been operated, a circuitwill again be completed for the operation or" relay 6&3 and the steppingmagnet 5|4 will cause the stepping switch to advance to the firstterminal on which the associated skip key has not been operated.

At the end of approximately .7 of a second after the release of relay652 condenser 'III will `again be charged to the potential required toinitiate a discharge current through the-anode circuit of tube H and theWinding of relay 103. The operation of relay 103 at this time againcompletes a circuit for the operation of relay 602. The reoperation ofrelay 602 causes relay 505 to release.

The reoperation of relay 502 again completes a circuit for the operationof stepping magnet 531 which magnet in operating permits the reoperationof relay 104. Relay 104 operates and interrupts the operating circuit ofmagnet 501, thus permitting this magnet to release and advance the brusharms 50i through 505, inclusive, to their third position. The operationof relay 104 again connects ground to the right-hand terminal ofcondenser 'FII and thus causes the release of l relay 103. Relay 103 inreleasing again permits relay 602 to release and remove ground from theright-hand terminal of condenser 1H which terminal again starts tocharge to the potential required to again initiate a discharge throughtube H0.

Meantime, however, the release of relay BSZ interrupts the lockingcircuit of relay 104 and permits this relay to' release. The release ofrelay 6(22 also again completes a circuit for the operation of thedistributor start magnet IEM and permits the distributor shaft |ii torotate through another revolution. This time the brush arms 50| through506, inclusive, are in their No. 3 position Where they conditionthe'co'ntacts controlled by the distributor shaft I 95'! so that a linefeed code combination is transmitted over the receiving channel of theparty line at this time.

Near the beginning of the vrevolution of shaft |05I contacts |050 willclose and complete a circuitfor the operation of relay 505 which relayoperates and completes a circuit for maintaining itself operated under-control of relay 602. The operation of relay 605 also interrupts thecircuit of the distributor release'magnet |fl1 and permits this magnetto release and stop the transmitter shaft I05I at the end of therevolution during which the line feed code combination was transmitted.f

At the end of the third .7 second time interval relay 103 will againoperate and complete a circuit for the reoperation of relay G02. Relay602 in operatingat this time interrupts the locking circuit of relayy6135 and permits relay 605 to release. The operation of relay 552 atthis time again completes a circuit for they operation of the steppingmagnet 501. The operation of the stepping magnet 501 permits theoperation of relay 104. The operation of relay 10ft interrupts theoperating circuit oi magnet 501 and permitsthis magnet to release andadvance the brush arms through 505 to their No. i position. Theoperation of relay |04 connects ground to the righthand terminal ofcondenser 1II and thus interrupts the current flowing through theanodecathode circuit of tube 1I0 and the winding of relay 103 thuscausing the release-of relay 103. Relay 103 in releasing interrupts theoperating circuit of relay 062. Relay 602m turn releases after a shortinterval of time and removes ground from the right-handwvinding terminalof condenser 1I I. Inasmuch` as brush arm 504 is now in its No. 4position the charging circuit of the right-hand terminal of condenser 1!I noW extends from battery 1 I through the right-hand portion of`resistance .1M and resistance 552 in parallel with resistance The timeconstants of condenser 1I I, together` with the constants of thecircuits of tube 1 iii, are such that it requires approximately1.9.seconds for the right-hand terminal of condenser 1I l to be chargedtothe value required to initiate the discharge through tube 1I0.

Meantime the release of relay 602 again completes a circuit for theoperation of the distributor release magnet |041 thus permitting thedistributor shaft I05| to rotate through a third revolution. Atths timethe brush arms 50| through 5% are in their No. 4 position. Consequentlythe code combination transmitted by the distributor at this time will bedetermined by the connections to the terminals of the banks cooperatingwith brushes 508, 509, 5I0 and 5I3 upon which these brushes are restingat this time. Near the beginning of the revolution of shaft |05|contacts |050 will again be closed and complete a circuit for theoperation of relay 605. Relay 605 completes a circuit for maintainingitself operated under control of relay 602 and interrupts the operatingcircuit of the releasemagnet |041 thus insuring that thedistributorshaft I05| will stop at the end of the third revolution.

On the transmission of this third code combination a complete set oftransmitter start signals has been transmitted over the receivingchannel of the party line to which the transmitter start circuit isconnected. If the transmitter to which this set of transmitter startsignals has been assignedfis provided with storage material availablefor transmission, transmission to the central oiiice will be initiatedtherefrom some time during the 1.9 second charging interval of condenser1|I or during the subsequent .7 second charging interval to bedescribed. At the the upper Winding of relay 104, thus permitting 'thisrelay to operate and interrupt the operating Vcircuit of the steppingmagnet 501. The release of magnet 501 causes the brush arms 501 through506 to advance to their No. 5 position.

The operation of relay 104 also completes a circuit for connectingground to the right-hand terminal of condenser 11 l thus causing relay-103 to release which in turn causes the release of relay 602.

The release of relay 602 removes ground from the right-hand terminal ofcondenser 111 and thus permits this terminal to again be charged frombattery 116 through resistances 553 in parallel with 551. The timeconstant of this charging circuit, as pointed out above, isapproximately .7 of a second.

With brush arm 501 in its No. position a circuit is completed for theoperation of relay 601. With relay 601 operated a circuity is completedfrom conductor 2136 extending from the incoming line circuit to thewinding of relay 606. If the corresponding transmitter has started totransmit message material, relay 606 will operate and interrupt thelocking circuit of relay 102 thus permitting relay 102 to release.

The operation of relay 606 also completes a circuit for the operation ofthe stepping magnet 511 thus permitting this magnet to operate andremove a short circuit from around the lower winding of relay 609,whereupon relay 609 operates and interrupts the operating circuit ofstepping magnet 511 thus causing the advance of brush arms 515 and 516.The above cycle of operations of magnet 511 and relay 609 is repeateduntil the brush arms 516 and 515 rest in the same position as the brusharms 501 through 506. At this time a circuit is completed through theupper winding of relay 609 for maintaining this relay operated. Iheoperation of relay 606 interrupts the operating circuit of relay 105 andpermits relay 105 to be released. Release of relay 105 interrupts theoperating circuit of relay 101 and either causes this relay to releaseor prevents its operation.

The release of relay 102 as described above interrupts the operatingcircuit of relays 80| and 914 which in turn allows the operation of thetransmitting device shown in Fig. under vcontrol of tape 1030 and thusresumes transmission of the interrupted message.

The release of relay 102 also connects ground to the right-hand terminalof condenser 11 1, thus discharging the condenser and interrupting theanode current of tube 110 and preventing the operaton of relay 103.

' Thereafter circuits are maintained in this condition so long as thetransmission is received from any transmitter associated with the partyline. At the end of the transmission from this transmitter, or inresponse to a pause in transmission longer than a predetermined length,ground will be removed from lead 2136 by incoming line circuit andinterrupt the operating circuit of relay 606. The release of relay 606at this time will cause relay 61 1 to operate as described above andadvance the brush arms 501 `through 506 to their No. 1 position wherethe above cycle of operation 12 oi.' the transmitter start circuit willbe repeated.

Assume now that the transmitter start circuit has functioned asdescribed above and has transmitted the third character or codecombination of a transmitter start pattern during the 1.9 seconds duringwhich brush arms 501 through 506 arev in their No. 4 position and thatthereafter these brush arms advanced to a No. 5 position and caused theoperation of relay 601 as described above. In thisv case, however,assume that no material was available for transmission from thetransmitter assigned to the particular transmitter start pattern whichhas just been transmitted from the transmitter start circuit. Underthese circumstances, no signals can be received by the incoming linecircuit during the .'7 of a second during which brush arms 60| through506 remain in their No. 5 position. Consequently no ground will beconnected to lead 2136 during this time and relay 606 will not operate.At the end of the .7 second time interval, the potential on theright-hand terminal of condenser 11| will reach the value required toinitiate a iiow of current through the anode-cathode path and cause theoperation of relay 103. Relay 103 then operating completes the circuitfor the operation of relay 602. Relay 602 in operating at this timecompletes the circuit for the operation of the stepping magnet 501 whichmagnet in operating removes a short circuit from around the upperwinding of relay 104 and permits this relay to operate. The operation ofrelay 104 interrupts the operating circuit and stepping magnet 501 andpermits this magnet to release and advances brush arms 501 through 506to the No. 6 position. The operation of relay 104 also connects groundto the right-hand terminal of condenser 111 thus discharging thiscondenser and causing the release of relays 103 and 602.

When brush arm 501 reaches its No. 6 position, a circuit is complete forthe operation of relay 611 and brush arms 501 through 506 re- 'stored totheir No. 1 position again. The above cycle of operation is thencompleted and a different transmitter start pattern transmitted causingthe brush arms 508 through 513, inclusive, to advance one step duringeach cycle of operation of brush arms 50| through 506. Conse' quently, adifferent transmitter start circuit pattern is usually transmittedduring each cycle of operation of brush arms 501 through 506, unless, ofcourse, the same code combination is set up on adjacent terminals of thebanks cooperating with brush arms 508, 509, 510 and 513.

When the brush arms 508 through 513 step off of the No. 10 terminals andonto the N terminals brush arm 511 completes a circuit for the operationof relay 595. Relay 595 in operating completes circuits for theoperation of stepping magnets 593 and 594 and relay 603. Relay 603 inoperating completes a circuit for the operation of stepping magnet 514.The operaf tion of magnets 593 and 594 interrupts the operating circuitof relay 595. Relay 595 in turn causes the release of magnets 593 and594 and relay 603. Relay 603 in releasing causes the release of magnet514. The release of magnets 514, 593 and 594 causes the respective brusharms 508 through 513 and 511 through 511 to be advanced one step.Consequently brush arms 508 through 513 are advanced from their No. 10position to their No. l position without remaining in their N position.

The above cycle of operations of the transmitter start circuit isrepeated until either trans- 13 mission is started from one of thetransmitters, or until brush arms 508 through 513 are advanced to thesame position as brush arms 515 and 516. It will be recalled that brusharms 515 and 516 were advanced to the position indicating the lasttransmitter to transmit. When brush arms 508 through 513 have advancedthrough al1 of their positions and have again returned to the positionassigned to the last transmitter to transmit without finding any storedmaterial available for transmission from any of the transmitters, theyWill cause the transmitter start circuit pattern assigned to thattransmitter to be retransmitted to the transmitter start circuit.However, with brush arms 50| through 506 in their No. l position causingbrush arms 508 through 513 to advance to the same position as brush arms515 and 516, a circuit will be completed through the upper winding ofrelay 609 thus causing the operation of this relay. Inasmuch as relay105 has been operated during the testing of all the other transmitters,the operation of relay 609 completes a circuit for the operation ofrelay 191. Thereafter the brush arms 501 through 506 are advanced totheir No. 1, No. 2, No. 3 and No. e positions during the transmismissionof respective portions of transmitter start pattern assigned to the lasttransmitter which transmitted. If transmission is not initiated fromthis transmitter during the time brush arms 501 through 506 are in theirNo. 5 position, then at the end of the .'7 seconden the No. 5 positionof brush arms 501 through 506, relay 103 will operate and complete thecircuit for the operation of relay 602. operate and cause brush arms 501through 506 to be advanced to the No. 6 position due to the successiveoperation of stepping magnet 501 and relay '104 and the subsequentrelease of magnet 501 and relay 194. This time relay '101 is operatedand consequently relay 61 1 will not operate. The right-hand terminalcondenser 111, which Was DleVOuSly discharged due to the combinedoperation oi relays 602 and 104, will again start the charge frombattery 116. At this time, hoW- ever, the charging circuit extendsthrough resistance 551 only. The value of resistance 551, together Awiththe value of condenser 111 and the other constants of the tube 110 andassociated circuits are such as to require approximately two minutes forcondenser 111 to be charged suriiciently to cause the operation ofrelays 103 and 602. Upon the operation of these relays, brush arms 501through 506 will be advanced to the next position and the above cycle ofoperations completed until brush arms 501 through 506 are advancedthrough the intervening positions to their No. 1 position. As describedin the above-identified application, Branson et al, a suitable number oisteps of two seconds may be provided depending upon the stripping orconnections to the contact terminals cooperating with brush arm 502.Furthermore the number of steps may be varied depending upon whether ornot the outgoing or receiving channel of the associated party line isemployed in the transmission of messages to some one or more of thestations associated with the party line.

Thus during periods when no message material is available fortransmission, each of the transmitters is tested in rotation and thenthe circuits pause for a predetermined interval of time, after which thetransmitters are again tested. f

Relay 502 will i As` indicated above, if it is desired to prevent thetesting of any of the transmitters, skip keys 541 through 550 have beenprovided. If any of these keys is operated, the corresponding relays 581through 590 are also operated. As described above, when brush arms 501through 506 are advanced to their No. 2 position and brush arms 598through 513 are advanced to terminals, the corresponding skip keys andassociated skiprelays 581 through 590 of which are operated, -brush arms508 through 513 will be advanced to their next position or will beadvanced step by step until they rest upon a set of terminals associatedwith some transmitter or station the skip relay of which has-not beoperated. Thus it is possible to prevent testing of any of thetransmitters during the operation of transmitter start circuit by theoperation of any of the skip keys 541 through 550.

In accordance with the present invention, provision has been made tocause the transmitter start circuit to automatically skip any one ormore of the transmitters during any cycle of operation of thetransmitter start circuit. Means has also been provided for varying thetransmitters skipped during different cycles of operation oi thetransmitter` start circuit. This additional equipment comprises a groupof brush arms 511 through 511 and associated banks of contacts, as shownin Fig. 5. It will be readily understood by persons skilled in the artthat a brush arm and an associated group of contacts is provided foreach of the stations or transmitters to be started in addition to thebrush arm 511. These brush arms are advanced by means of steppingmagnets 593 and 594 or additional magnets to these if more are required.A recycle key 591 has been provided and when operated completes thecircuit for the operation of relay 592. Relay 592 when operatingcompletes the circuit for maintaining itself operated if brush arm 511is in any position other than its normal or No. 1 position. Theoperation of relay 592 also completes the circuit for the operation ofthe driving relay 595 if brush arm 5,11 is in any position other thanits No. 1 position. The operation of relay 595 completes the circuit foroperation of stepping magnets 593 and 594. The operation of thesemagnets interrupts the operating circuit of relay 595, permits thisrelay to release, and releases the magnets 593 and 594, thus advancingall the brush arms 511 through 511 to their next position. The abovecycle of operation is then repeated until brush arms 511 through 511 arerestored to their initial or No. 1 position. f

If key 518 is operated to the position shown in the drawings when key519 is operated then each time brush arms 508 through 513 are advancedfrom their No.- 10 position through their N position to their No. 1position, a circuit will be completed for the operation of relay 595 andthe subsequent advance of brush arms 511 through 511 to their nextposition. The terminals cooperating with the brush arms 512 through 511,inclusive, are connected to the upper windings of relays 531 through590, inclusive, and consequently depending upon the connection ofterminals to these windings, relays .581 through 590 will be operatedwhen the brush arms 512 through 51-1 are in various of their positions.When'these relays are operated, they will cause the transmitter startcircuit to skip the testing of the associated transmitter. Thus byproperly connecting the bank terminals associated with the brush arms512 through 51-'1 to the upper windings of the skip relays 58| through590, the testing of the various transmitters will be skipped during eachcycle of operation of the transmitter start circuit and the respectivetransmitters skipped will be automatically varied in accordance with theconnections to the bank terminals cooperatingr with brush arms 512through 511.

The 'automatic skip equipment, in accordance withthis invention, may bedisabled by the operation of key 518 to the position opposite to theposition shown in the drawings. The operation of key 518 to thatposition disables the recycle key 59! and prevents the operation of theskip relays 58! through 590 under control of brush arms 512 through 511and thus renders the automatic skip equipment ineffective. Consequently,under these conditions the transmitter start circuit and equipmentoperates substantially as set forth in the above-identied application ofBranson et al, incorporated herein.

'I'his additional equipment in no way interferes with the operation ofthe transmitter start circuit during manual operation of the transmitterstart circuit because battery is connected to the upper windings of skiprelays 58| through 590 only during automatic operation by the operationof relay 608 which relay is operated only during automatic operation ofthe transmitter start circuits.

The transmitter start circuit shown in detail in the drawings providesnumerous other features and manners of operation which are fully setforth in the above-identiiied application of Branson et al. However,inasmuch as these other features do not affect the operation of theautomatic skip feature, their` description has not been repeated herein.It is to be understood, however, that these features are provided andoperate in substantially the same manner as described in theabove-identied application of Branson et al.

What is claimed is:

1. In a telegraph system, a plurality of tape controlled transmittersfor transmitting over a common channel of transmission, a controlcircuit for testing said transmitters one at a time inr sequence for thepresence of stored message material available for transmission,apparatus for causing said control circuit to skip and thereby vomittesting of any one or more of said transmitters, and apparatus forautomatically changing said control circuit to change the transmitter ortransmitters skipped during successive sequences of testing saidtransmitters.

2. In a telegraph system, a plurality of record controlled transmittersarranged to transmit over a common channel of transmission, atransmitter start circuit for cyclically testing each of saidtransmitters for record material available for transmission, apparatusfor causing` said start circuit to omit testing of predetermined ones ofsaid transmitters, and apparatus operativeincident to the operation ofsaid start circuit for changing the transmitter or transmitters skippedduring successive cycles of testing said transmitters. K

3. In a telegraph system, a pluralityof record controlled transmittersarranged tol transmitover a common channel of transmission, atransmitter start circuit for cyclically'` testing each of said@transmitters for record material available for transmission, apparatusfor causing said start circuit to omit testing of any of saidtransmitters, .and apparatus for automatically changing the individualtransmitters skipped over by said start v16 circuit during differentones of said cycles of operation thereof.

4. In a telegraph system, a plurality of geographically separatedstorage controlled transmitters, a common telegraph transmission channelextending .to each of said transmitters, a start circuit for testingsaid transmitters one at a time and in rotation for the presence ofstorage material available for transmission therefrom one at a time andin successive order, automatically controlled apparatus for causing saidstart circuit to skip and thereby omit testing different ones of saidtransmitters during predetermined sequences of testing, v

5. In a telegraph system, a plurality of telegraph transmittersassociated with a channel of transmission for transmitting thereover oneat la time, a control circuit for transmitting to said transmitters aplurality of control patterns of code combinations for selectivelyinitiating transmission from any of said transmitters and automaticmeans for automatically varying the order of supplying said patterns tosaid control circuit.

6. In a telegraph system, a plurality of geographically separatedtelegraph transmitters associated with a channel of telegraphtransmission for transmitting thereover one at e, time, a transmitterstart circuit for transmitting to said transmitters a plurality ofcontrol patterns of code combinations for selectively initiatingtransmission from any one of said transmitters and automatic means forsupplying said patterns to said transmitter start circuit one at a timeand in rotation, and control apparatus operative concurrently with saidtransmitter start circuit for reducing the supply of certain of saidpatterns to said transmitter start circuit.

7. In a telegraph System, a plurality of tape controlled transmitters, atelegraph transmission -channel extending to all of said transmitters,switching apparatus for connecting each of said transmitters to saidchannel, a transmitter start circuit for controlling said switchingapparatus comprising apparatus for sending the transmitter startpatterns Aassigned to each of said transmitters one at a time and inrotation, and automatically controlled apparatus for varying thefrequency of supply of predetermined of said patterns duringpredetermined rotations of the operation of said transmitter startcircuit,

8. In a telegraph system, a plurality of tape controlled transmitters, atelegraph transmission channel extending to all of said transmitters,switching apparatus for connecting each of said transmitters to saidchannel, a transmitter start circuit for controlling said switchingapparatus comprising apparatus for sending transmitter start patternsassigned to each of said transmitters one at a time and in rotation,apparatus for preventing the supply of any of said patterns during anyrotation of the operation of said transmitter start circuit, andautomatically .controlled apparatus for cyclically varying the number oftransmitters omitted during the operation of said transmitter startcircuit. Y

9. In a telegraph system, a plurality of tape controlled telegraphtransmitters, e, telegraph transmission channel extending to all of saidtransmitters, switching apparatus for connecting each of saidtransmitters to said channel, a transmitter start circuit forcontrolling said switching apparatus comprising apparatus for sendingthev transmitter start patterns assigned to each of said transmittersone at a time and in rotation, apparatus for causing said start circuitto skip transmission of said start patterns, manually controlledapparatus for designating the patterns to be skipped by said startcircuit, and automatic apparatus to automatically vary additionalpatterns skipped by said start circuit.

10. An automatic telegraph transmitting arrangement for transmitting aseries of telegraph signal patterns one after another, automaticskipping means for causing said transmitting arrangement to skip thetransmission of different ones of said telegraph signal patterns, andmeans automatically operable between said series of patterns to changethe patterns to be skipped during the transmission of the succeedingseries cf patterns.

11. An automatic telegraph transmitting |arrangement for cyclicallytransmitting a series of different telegraph signal patterns one afteranother, apparatus for causing said telegraph larrangement to omit thetransmission of any of said patterns, manual control means fordesignating the patterns to be omitted, and automatic control means forautomatically designating the patterns to be omitted during diierentcycles of operation of said transmitting arrangement.

12. In a telegraph system, a plurality of record controlled transmittersarranged to transmit over a common channel of transmission, atransmitter start circuit for cyclically testing said transmitters forrecord material available for transmission, and apparatus forautomatically changing the number of times at which certain of saidtransmitters lare tested for record material available for transmission,as compared to the number of times other transmitters are tested.

13. In a telegraph system, a plurality of telegraph transmittersassociated With a channel of transmission for transmitting thereover oneat a time, la control circuit for transmitting to said transmitters aplurality of control patterns of code combinations for selectivelyinitiating transmission from any of said transmitters, and apparatusoperative incident to the operation of said control circuit forautomatically changing the number of times certain of said controlpatterns are transmitted relative to the number of times others of saidcontrol patterns are transmitted.

14. In a telegraph system, a plurality of record controlledtransmitters, a common channel of transmission extending adjacent saidtransmitters, switching equipment adjacent said transmitters forselectively connecting said transmitters to said channel one at a time,a transmitter start circuit for cyclically transmitting a plurality ofcontrol patterns of code combinations for controlling said switchingapparatus to selectively test said transmitters for record materialavailable for transmission, contro1 apparatus for said 18 transmitterstart circuit for automatically varying the relative number of occasionsof testing of certain of said transmitters for record material availablefor transmission.

15. In a telegraph system, a plurality of tape controlled transmittersat least one of which is located remote from the other of saidtransmitters, a telegraph transmission channel extending to all of saidtransmitters, switching apparatus for connecting each of saidtransmitters to said channel, a cyclically operating transmitter startcircuit for controlling said switching apparatus, and apparatusoperative incident to cycles of operation of said transmitter startcircuit for causing certain of sai-d transmitters to be connected tosaid channel less frequently on some cycles than others of saidtransmitters.

16. In a telegraph system, a plurality of record controlled transmittersarranged to transmit over y a common channel of transmission, atransmitter start circuit for testing each of said transmitters forrecord material available for transmission and apparatus operativeincident to the operation of said transmitter start circuit forcyclically changing the order in which said transmitters are tested forrecord material available for transmission.

17. In a telegraph system, a plurality of record controlled transmittersarranged t0 transmit over a common channel of transmission, atransmitter start circuit for cyclically testing each of saidtransmitters for record material available for transmission, apparatusfor controlling said start circuit for testing certain of saidtransmitters oftener than others of said transmitters, and

means for automatically changing in accordance with a predeterminedschedule the number of times a predetermined transmitter is testedrelative to the number of times others of said transmitters are testedfor record material available for transmission.

18. In a telegraph system, a plurality of tape controlled transmitters,a telegraph transmission channel extending to all of said transmitters,switching apparatus for connecting each of said transmitters to saidchannel, a transmitter start circuit for controlling said switchingapparatus comprising equipment for sending a plurality of differenttransmitter st-art patterns each of which is assigned to one of saidtransmitters, apparatus operative incident to the operation of saidtransmitter start circuit for causing one or more of said patterns to betransmitted more frequently than others of said patterns, and means forchanging the transmission of certain of said patterns relative totransmission of others of said i patterns.

